Near-field transducer dielectric wrap for reducing heat

ABSTRACT

An apparatus comprises a write pole, a waveguide core, and a near-field transducer (NFT) positioned between the write pole and the waveguide core. The NFT comprises a heatsink portion, an enlarged portion, and a peg comprising a refractory metal and extending from the enlarged portion toward a media-facing surface. A first surface of the peg is substantially coplanar with a first surface of the enlarged portion and the first surface of the enlarged portion shares an interface with the heatsink portion. A first dielectric layer is positioned between the peg and the write pole, and a first adhesion layer is positioned between the peg and the first dielectric layer. In addition, a second dielectric layer is disposed on an entire surface of the NFT opposing the media-facing surface, and a second adhesion layer is positioned between the NFT and the second dielectric layer.

SUMMARY

Embodiments of the disclosure are directed to an apparatus comprising awrite pole, a waveguide core, and a near-field transducer (NFT)positioned between the write pole and the waveguide core. The NFTcomprises a heatsink portion, an enlarged portion, and a peg comprisinga refractory metal and extending from the enlarged portion toward amedia-facing surface. A first surface of the peg is substantiallycoplanar with a first surface of the enlarged portion and the firstsurface of the enlarged portion shares an interface with the heatsinkportion. The apparatus further includes a first dielectric layerpositioned between the peg and the write pole, a first adhesion layerpositioned between the peg and the first dielectric layer, a seconddielectric layer disposed on an entire surface of the NFT opposing themedia-facing surface, and a second adhesion layer positioned between theNFT and the second dielectric layer.

Further embodiments are directed to an apparatus comprising a writepole, a waveguide core, and an NFT positioned between the write pole andthe waveguide core. The NFT comprises a heatsink portion, an enlargedportion, and a peg comprising a refractory metal and extending from theenlarged portion toward a media-facing surface. A first surface of thepeg is substantially coplanar with a first surface of the enlargedportion and the first surface of the enlarged portion shares aninterface with the heatsink portion. A first dielectric layer ispositioned between the NFT and the write pole, and a second dielectriclayer is positioned between the NFT and the waveguide core, wherein atleast one of the dielectric layers has a refractive index less than 1.5.

Additional embodiments are directed to an apparatus comprising a writepole, a waveguide core, and an NFT positioned between the write pole andthe waveguide core.

The NFT comprises a heatsink portion, an enlarged portion, and a pegcomprising a refractory metal and extending from the enlarged portiontoward a media-facing surface. A first surface of the peg issubstantially coplanar with a first surface of the enlarged portion andthe first surface of the enlarged portion shares an interface with theheatsink portion. A first dielectric layer is positioned between the pegand the write pole, and a second dielectric layer is positioned betweenthe NFT and the waveguide core. The second dielectric layer comprises abi-layer structure having a first dielectric material proximate the pegand a second dielectric material proximate the waveguide core.

The above summary is not intended to describe each disclosed embodimentor every implementation of the present disclosure. The figures and thedetailed description below more particularly exemplify illustrativeembodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The discussion below refers to the following figures, wherein the samereference number may be used to identify the similar/same component inmultiple figures. However, the use of a number to refer to a componentin a given figure is not intended to limit the component in anotherfigure labeled with the same number. The figures are not necessarily toscale.

FIG. 1 is a perspective view of a HAMR slider assembly according toembodiments discussed herein;

FIG. 2 is a cross-sectional view of a slider along a down-track plane,according to embodiments discussed herein;

FIG. 3A is a partial perspective view of a baseline near-fieldtransducer configuration according to embodiments discussed herein;

FIG. 3B is a partial perspective view of a partially wrapped near-fieldtransducer according to embodiments discussed herein;

FIG. 3C is a partial perspective view of a partially wrapped near-fieldtransducer according to embodiments discussed herein;

FIG. 3D is a partial perspective view of a fully wrapped near-fieldtransducer according to embodiments discussed herein;

FIG. 4 is a partial perspective view of the slider of FIG. 3B showingadhesion layers according to embodiments discussed herein;

FIG. 5A is a cross-sectional view of an example thermal gradientproduced by a non-recessed near-field transducer configuration accordingto embodiments discussed herein;

FIG. 5B is a cross-sectional view of an example thermal gradientproduced by a recessed near-field transducer configuration according toembodiments discussed herein;

FIG. 6A is a partial perspective view of a recessed, fully wrappednear-field transducer according to embodiments discussed herein;

FIG. 6B is a partial perspective view of a recessed, partially wrappednear-field transducer according to embodiments discussed herein;

FIG. 7A is a partial perspective view of a recessed, fully wrappednear-field transducer including a sunken disc according to embodimentsdiscussed herein; and

FIG. 7B is a partial perspective view of a recessed, partially wrappednear-field transducer including a sunken disc according to embodimentsdiscussed herein.

DETAILED DESCRIPTION

The present disclosure is generally related to heat-assisted magneticrecording (HAMR), also referred to as energy-assisted magnetic recording(EAMR), thermally-assisted recording (TAR), thermally-assisted magneticrecording (TAMR), etc. In a HAMR device, a source of optical energy(e.g., a laser diode) is integrated with a recording head and couplesoptical energy to a waveguide or other light transmission path. Thewaveguide delivers the optical energy to a near-field transducer (NFT).The NFT concentrates the optical energy into a tiny optical spot in arecording layer of a magnetic recording medium, which raises themedium's temperature locally, reducing the writing magnetic fieldrequired for high-density recording.

Generally, the NFT is formed by depositing one or more thin-films of aplasmonic material such as gold, silver, copper, aluminum, etc., at ornear an integrated optics waveguide or some other light/energy deliverysystem. The laser light, delivered via the waveguide, generates asurface plasmon field on the portions of the NFT exposed to the light.The NFT is shaped such that the surface plasmons are directed out of asurface of the write head onto a magnetic recording medium.

Due to the intensity of the laser light and the small size of the NFT,the NFT and surrounding material are subject to a significant rise intemperature during writing operations. Over time, this can affectintegrity of the NFT, for example, causing it to become misshapen. Otherevents, such as contact between the read/write head and a recordingmedium, and/or with contamination on the recording medium, etc., mayalso degrade the operation of the NFT and nearby optical components. Thehigh NFT temperatures thereby decrease the reliability of the HAMRread/write head and the effective service life of the head (i.e., thenumber of laser-on hours). In view of this, embodiments described hereinare directed to reducing the NFT temperature by introducing and/orincreasing the amount of low optical index materials proximate the NFT.

In reference now to FIG. 1, a perspective view shows a read/write head100 according to an example embodiment. The read/write head 100 may beused in a magnetic data storage device, e.g., HAMR hard disk drive. Theread/write head 100 may also be referred to herein interchangeably as aslider, head, write head, read head, recording head, etc. The read/writehead 100 has a slider body 102 with read/write transducers 108 at atrailing edge 104 that are held proximate to a surface of a magneticrecording medium (not shown), e.g., a magnetic disk.

The illustrated read/write head 100 is configured as a HAMR device, andso includes additional components that form a hot spot on the recordingmedium near the read/write transducers 108. These HAMR componentsinclude an energy source 106 (e.g., laser diode) and a waveguide 110.The waveguide 110 delivers electromagnetic energy from the energy source106 to a NFT that is part of the read/write transducers 108. The NFTachieves surface plasmon resonance and directs the energy out of amedia-facing surface 112 to create a small hot spot in the recordingmedium.

In FIG. 2, a cross-sectional view shows details of a slider body 102according to an example embodiment. The waveguide 110 includes a core200, top cladding layer 202, side cladding layer 204, and bottomcladding 206. A waveguide input coupler 201 at a top surface 203 of theslider body 102 couples light from the light source 106 to the waveguide110. The waveguide input coupler 201 receives light from the lightsource 106 and transfers the light to the core 200. The waveguide core200 is made of dielectric materials of high index of refraction, forinstance, AlN (aluminum nitride), Ta₂O₅ (tantalum oxide), TiO₂ (titaniumoxide), Nb₂O₅ (niobium oxide), Si₃N₄ (silicon nitride), SiC (siliconcarbon), Y₂O₃ (yttrium oxide), ZnSe (zinc selenide), ZnS (zinc sulfide),ZnTe (zinc telluride), Ba₄Ti₃O₁₂ (barium titanate), GaP (galliumphosphide), CuO₂ (copper oxide), and Si (silicon). The cladding layers202, 204, 206 are each formed of a dielectric material having arefractive index lower than the core 200. The cladding can be, forinstance, Al₂O₃ (aluminum oxide), SiO (silicon oxide), and SiO₂(silica). As discussed further below, cladding layers 202 and 204 cancomprise different materials, or the same materials.

The core 200 delivers light to an NFT 208 that is located within theside cladding layer 204 at the media-facing surface 112. A write pole210 (which is a distal part of a magnetic write transducer) is locatednear the NFT 208. The magnetic write transducer may also include a yoke,magnetic coil, return pole, etc. (not shown). A heat sink 214 thermallycouples the NFT 208 to the write pole 210. The magnetic coil induces amagnetic field through the write pole 210 in response to an appliedcurrent. During recording, an enlarged portion 208 a (e.g., a roundeddisk) of the NFT 208 achieves surface plasmon resonance in response tolight delivered from the core 200, and the plasmons are tunneled via apeg 208 b out of the media-facing surface 112. The energy delivered fromthe NFT 208 forms a hotspot 220 within a recording layer of a movingrecording medium 222. The write pole 210 sets a magnetic orientation inthe hotspot 220, thereby writing data to the recording medium.

As noted above, the NFT 208 reaches high temperatures during recording,and over time, this can cause instability. While the enlarged part 208 aof the NFT 208 is generally formed from a plasmonic material such as Au(gold), Ag (silver), Cu (copper), Al (aluminum), or alloys thereof, thepeg 208 b may be formed from a high-melting-point material, such as arefractory metal (including Rh (rhodium), Ir (iridium), Pt (platinum),Pd (palladium), or alloys thereof, etc.), to improve peg thermalstability. In existing designs, one side of the peg 208 b is in directcontact with a dielectric. Embodiments described herein have both thepeg 208 b and the enlarged portion 208 a wrapped in a low optical index(e.g., less than 1.5) dielectric material. The low index dielectricreduces NFT absorption resulting in reduced NFT operating temperatures.

FIGS. 3A-D illustrate perspective cross-sectional views of a HAMR sliderhaving different configurations of low index dielectric material. InFIG. 3A, a baseline configuration is shown where an NFT is positionedbetween a write pole 310 and a waveguide core 300. The NFT comprises anenlarged portion 308 a, a peg 308 b, and a heatsink 314. The peg 308 bextends from the enlarged portion 308 a toward the media-facing, orair-bearing, surface (ABS) 312. Portions of the waveguide cladding areshown proximate an NFT surface opposite the ABS, including a topcladding layer 302 and a side cladding layer 304. The side claddinglayer includes a layer 304 a that is disposed between the NFT and thewaveguide core 300, and the layer 304 a can be referred to as the coreto NFT spacing (CNS) layer. The CNS layer can be about 10 to 60 nm,about 15 to 30 nm, or about 15-25 nm. Also, the layer 306 locatedbetween the peg 308 b and the write pole 310 is referred to herein asthe NFT to pole spacing (NPS) layer. While the NFT is generallysurrounded by dielectric material, the respective refractive indices ofthose materials in combination with the NFT materials affect thetemperature of the NFT.

The NFTs discussed herein have a peg and enlarged portion (e.g., disk)configuration, where the enlarged portion 308 a and heatsink 314 arecomprised of a relatively soft plasmonic material (e.g., Au, Ag, Cu, Al,and alloys thereof). However, the NFT can have any variety ofconfigurations including gap type and peg only NFTs. In each of theconfigurations, the peg 308 b is comprised of a refractory metal (e.g.,Rh, Ir, Pd, Pt, and alloys thereof). Since a refractory metal has ahigher melting point than a soft plasmonic material, an NFT with arefractory metal peg can operate at higher temperatures than an NFT witha soft plasmonic peg. A refractory metal is also a useful peg materialsince it is hard and resistant to corrosion. In certain embodiments, theenlarged portion 308 a comprises gold, and the peg 308 b comprisesrhodium.

In the baseline configuration of FIG. 3A, the NFT is largely surrounded,or wrapped, in alumina. The side cladding 304, CNS layer 304 a, and theNPS layer 306 are all alumina (Al₂O₃) while the top cladding 302 issilica (SiO₂). A dielectric with a refractive index of less than 1.5 canreduce the temperature of the NFT. While alumina has an opticalrefractive index of 1.7682, silica has a refractive index of 1.4585. Thelower optical index dielectric (e.g., an index of less than 1.5) causessurface plasmon polaritons to have longer oscillation length into thesurrounding medium (e.g., dielectric). This improves the NFT efficiencyby requiring less laser current for HAMR writing. The reduced current,correlates to reduced NFT temperature and increased life and reliabilityfor the head.

In further embodiments, more surface area of the NFT is wrapped in alower refractive index material than the baseline configuration shown inFIG. 3A. FIG. 3B illustrates a configuration referred to herein asDesign I, where, in addition to the top cladding 302, the side cladding304 and the NPS layer 306 are replaced with silica. In FIG. 3B, the CNSlayer 304 a remains as alumina. FIG. 3C illustrates a configurationreferred to Design II, where a bi-layer structure is shown for the CNSlayer. While the CNS layer 304 a remains as alumina, the portion betweenthe peg 308 b and the bottom surface of the NFT, layer 304 b, isreplaced with silica. Thus, in FIG. 3C, the top cladding 302, the sidecladding 304, the NPS layer 306, and layer 304 b are comprised ofsilica. FIG. 3D illustrates a configuration referred to as Design III,which shows the NFT fully wrapped in silica. Here, the top cladding 302,the side cladding 304, the CNS layer 304 a, layer 304 b, and the NPSlayer 306 are comprised of silica.

The increased amount of lower index material (e.g., silica) reduces thetemperature of the NFT at both the peg 308 b and the enlarged portion308 a. Table 1 below shows the respective temperature differences forthe different designs, as compared with the baseline configuration.

TABLE 1 Configuration Peg ΔT (° C.) Disk ΔT (° C.) Design I −32 −18Design II −42 −22 Design III −54 −27Table 1 shows the temperature change for components of the respectivedielectric configurations with respect to reference temperaturesrecorded for the baseline configuration of FIG. 3A. For each component,peg 308 b and enlarged portion 308 a (e.g., disk), the temperaturereduced further with each increase in the amount of lower index materialpresent proximate the NFT. The lower refractive index material provideda 30-50° C. decrease in NFT temperature at the peg, and a 10-30° C.decrease in temperature at the enlarged portion 308 a.

In addition to the amount of low index dielectric present proximate theNFT, the exposed length of the peg can also influence the NFTtemperature. The exposed peg length is described herein by the breakpoint, which is the position on the peg that is in contact with theenlarged portion of the NFT nearest to the ABS. For example, a breakpoint of 30 nm indicates that 30 nm of the peg extends outward from theenlarged portion toward the ABS. In Table 2, the respective temperaturedifferences for the different designs are shown for NFT configurationshaving different break points.

TABLE 2 Configuration Break Point (nm) Peg ΔT (° C.) Disk ΔT (° C.)Design I 35 −32 −18 Design II 35 −42 −22 Design III 35 −54 −27 Design I40 −39 −22 Design II 40 −50 −27 Design III 40 −65 −32Table 2 shows the temperature change for components of the respectivedielectric configurations with respect to reference temperaturesrecorded for the baseline configuration. As can be seen, the first threelines of Table 2 correspond to the data of Table 1 indicating that theconfigurations tested in Table 1 each had a break point of 35 nm.However, as the break point is increased, e.g., by 5 nm, the temperaturereductions also increased. Again, for each component, peg 308 b andenlarged portion 308 a (e.g., disc), the temperature reduced furtherwith each increase in the amount of lower index material presentproximate the NFT and increase in the break point (e.g., exposed peglength). Therefore, the lower refractive index material could reduce thebreak point sensitivity of the NFT.

While silica's lower refractive index allows for temperature reductionin the NFT, silica and some soft plasmonic materials such as gold do notadhere well to each other. If the NFT and surrounding dielectric lackstructural integrity, the NFT can move or be prone to damage, which cancause the entire magnetic recording device to fail during processing oroperation. To improve the structural integrity of the NFT, an adhesionlayer is disposed between the enlarged portion and peg of the NFT andthe silica dielectric portions. As shown in FIG. 4, the configuration ofFIG. 3B includes an adhesion layer 320 along the enlarged portion 308 asurface opposite the ABS as well as an adhesion layer 322 between theNPS layer 306 and the enlarged portion 308 a and the peg 308 b. There isalso an adhesion layer between the top cladding 302 and the heatsink 314when the top cladding 302 comprises silica. For the configurations ofFIGS. 3C-D, additional adhesion layers are positioned at the interfaceof the silica and the NFT. For example, in FIG. 3C, an adhesion layerwould be disposed along the surface of the peg 308 b and the ABS-facingsurface of the enlarged portion 308 a. In FIG. 3D, an additionaladhesion layer would be disposed between the NPS layer 304 a and thesurface of the enlarged portion 308 a opposing the heatsink 314. Whilethe adhesion layers can comprise a variety of materials, an aluminalayer having a thickness of about 2 to 10 nm can effectively adhere theNFT to the surrounding silica dielectric.

Incorporating an increased amount of low refractive index materialproximate the NFT reduces the NFT temperature. In certain embodiments,the NFT design can further increase the amount of low refractive indexmaterial proximate the NFT to further reduce the NFT temperature. FIGS.5A-B illustrate the thermal gradient generated by various NFT designs.Both figures show an NFT proximate a write pole 510 at a slider ABS 512.The NFT includes a heatsink 514, an enlarged portion 508 a, and a peg508 b. An NPS layer 506 is located between the peg 508 b and the writepole 510. A first surface 509 b of the peg 508 b is substantiallycoplanar with a first surface 509 a of the enlarged portion 508 a andthe first surface 509 a of the enlarged portion 508 a shares aninterface 513 with the heatsink 514. In FIG. 5A, similar to the NFTconfigurations shown in FIGS. 3A-D, the enlarged portion 508 a includesan overhang section 508 c that extends along a surface of the peg 508 bproximate the NPS layer 506. The overhang section 508 c can have athickness of up to, or more than, about 20 nm. This configuration isreferred to as a non-recessed design. In FIG. 5B, the overhang section508 c is removed such that the peg 508 b has an increased interface withthe NPS layer 506. This is referred to as a recessed design. While theenlarged portion is shown as being larger in FIG. 5A as compared withFIG. 5B, this is to highlight the addition of the overhang section 508c. The figures are not to scale, and the remainder of the enlargedportion 508 a can be the same size, or vary, between a non-recessed andrecessed NFT design.

As shown by the arrow in FIG. 5A, heat generated by the peg 508 b and/orreflected from the recording medium, flows through the NFT toward theheatsink 514. In FIG. 5A, heat travels through the peg 508 b, into theoverhang section 508 c, and then into the heatsink 514. This path causesthe thermal gradient 516 to bloom or widen along the ABS. This canresult in a larger thermal spot on the recording medium and/or errors inreading or writing to the medium. Thus, a sharper, or more focused,thermal gradient provides for more efficient writing/reading operations.As shown by the arrow in FIG. 5B, reduction, or removal, of the overhangsection 508 c sharpens the thermal gradient 518. The increased amount oflow index dielectric in the NPS layer 506 helps direct the heat paththrough the peg 508 b toward the heatsink 514. The recessed design ofFIG. 5B has a more focused thermal gradient 518 as compared with thethermal gradient 516 of FIG. 5A, and would be expected to further reducethe operating temperature of the NFT.

FIGS. 6A-B illustrate perspective cross-sectional views of a HAMR sliderhaving a recessed NFT design with different configurations of low indexdielectric material. In FIG. 6A, a recessed NFT configuration is shownwhere an NFT is positioned between a write pole 610 and a waveguide core600. The NFT comprises an enlarged portion 608 a (e.g., a disc), a peg608 b, and a heatsink 614. The peg 608 b extends from the enlargedportion 608 a toward the media-facing, or air-bearing, surface (ABS)612. Portions of the waveguide cladding 604 are shown proximate an NFTsurface opposite the ABS 612. The waveguide cladding 604 includes alayer 604 a that is disposed between the NFT and the waveguide core 600,and the layer 604 a can be referred to as the core to NFT spacing (CNS)layer. The CNS layer can be about 10 to 60 nm, about 15 to 30 nm, orabout 15-25 nm. Also, the layer 606 located between the peg 608 b andthe write pole 610 is referred to herein as the NFT to pole spacing(NPS) layer. While the NFT is generally surrounded by dielectricmaterial, the respective refractive indices of those materials incombination with the NFT materials affects the temperature of the NFT.

The NFT design of FIG. 6A is a fully-wrapped recessed NFT configurationand is referred to as Design IV. The term “fully-wrapped” refers to theNFT being surrounded by low refractive index material (e.g., n≤1.5). Forexample, the waveguide cladding 604, CNS layer 604 a, and NPS 606 areall comprised of low refractive index material such as silica. As in thedesigns discussed above, the NFT heatsink 612 and enlarged portion 608 aare comprised of a soft plasmonic material such as gold, and the peg 608b is comprised of a refractory metal (e.g., Rh, Ir, Pd, Pt, and alloysthereof). In certain embodiments, the enlarged portion 608 a comprisesgold, and the peg 608 b comprises rhodium.

As discussed above, different designs can involve varying amounts of lowindex dielectric material proximate the NFT. In FIG. 6B, a configurationreferred to herein as Design V, a combination of dielectric materials isused proximate the NFT. Here, the CNS layer 604 a and 604 b, along withthe NPS layer 606 comprise a low index dielectric material (e.g.,n≤1.5). However, the waveguide cladding 604 and the layer 616 betweenthe CNS layer 604 a and NPS layer 606 comprise a higher refractive indexdielectric such as alumina. This provides a partially-wrapped, orsandwich configuration, of low-index dielectric material. In alternativeembodiments, the recessed NFT configuration can be implemented withvarying amounts of low index dielectric material proximate the NFT,including configurations similar to the designs described above inconnection with FIGS. 3A-C. Also, the recessed NFT configurations caninclude adhesion layers between any and/or all low index refractivematerial (e.g., silica) layers adjacent the NFT (e.g., adjacent goldand/or gold alloys and/or Rh).

As discussed above, the increased amount of lower index material (e.g.,silica) reduces the temperature of the NFT at the peg 308 b. While thedielectric wrap may be silica as discussed above, materials with a lowerrefractive index than alumina, or even silica, can further reduce theNFT temperature. For example, dielectric material having a refractiveindex of about 1.40 (e.g., MgF₂) or lower can further reduce the pegtemperature of the NFT. Table 3 below shows the respective NFT pegtemperature differences for different designs and materials.

TABLE 3 Dielectric Configuration Material Peg ΔT (° C.) FIG. 5B silica−37.4 Design IV silica −47 Design V silica −34 Design IV n = 1.40 −63

Table 3 shows the peg temperature change of the respective dielectricconfigurations and dielectric materials with respect to a referencetemperature recorded for the baseline configuration of FIG. 5B havingAl₂O₃ (alumina) as the dielectric. Again, for each design, thetemperature of the NFT peg 608 b reduced further with increased amountsof lower index material present proximate the NFT. The fully-wrappeddesign of FIG. 6A provided a greater reduction in temperature ascompared with the sandwiched design of FIG. 6B. In addition, the lowerindex material (n=1.40) provided an even further temperature reductionfor the design of FIG. 6A than silica in the same design.

Increasing the amount of lower index material present proximate the NFTalso reduces the peg temperature of other NFT designs. FIGS. 7A-Billustrate perspective cross-sectional views of a HAMR slider having asunken disc NFT configuration. The sunken disc 716 comprises NFTplasmonic material (e.g., gold) positioned below the peg 708 b. FIG. 7Ashows a “full anchor” design where the peg is part of a contiguous layerof the same material forming the peg 708 b and the enlarged portion 708a of the NFT. FIG. 7B shows an alternative, “stitched anchor” designwhere the peg 708 b and only a portion of the enlarged portion 708 ccomprise the same material (e.g., the front portion closest to the ABS),and the remaining portion of the enlarged portion 708 b comprises adifferent material (e.g., the same material as the sunken disc 716and/or the heatsink 714). The heatsink 714 is positioned in contact withthe enlarged portion of the NFT 708 a, can comprise a material differentfrom that of the NFT enlarged region 708 a (i.e., in the full anchor”design), and is recessed from the media-facing, or air-bearing, surface(ABS) 712. Similar to the configuration of FIG. 6A, the NFT 708 a-b ispositioned between a write pole 710 and a waveguide core 700. The peg708 b extends from the enlarged portion 708 a toward the ABS 712. Whilenot shown, the sunken disc configurations of FIGS. 7A-B include awaveguide and cladding as illustrated in the previous designs andconfigurations. While the NFT is generally surrounded by dielectricmaterial, the respective refractive indices of those materials incombination with the NFT materials affects the temperature of the NFT ina sunken disc configuration.

The NFT design of FIG. 7A is also referred to herein as Design VI. Asshown in FIG. 7A, the design can be a fully-wrapped NFT configuration.The term “fully-wrapped” refers to the NFT being surrounded by lowrefractive index material (e.g., n≤1.5). Here, being surrounded refersto low refractive index material in at least four areas: 1) between thepeg and the write pole, NPS 720, 2) underneath the sunken disc, CDS 726,3) underneath the peg and above the CDS, CNS 724, and 4) at the sides ofthe peg 708 b and enlarged region 708 a, 722. In addition, the waveguidecladding (not shown but to the left of the heatsink 714 as shown inprevious designs), can also be comprised of low refractive indexmaterial such as silica. As in the designs discussed above, the NFTheatsink 712, sunken disc 716, and, in certain embodiments, a portion ofthe enlarged portion 708 a are comprised of a soft plasmonic materialsuch as gold, and the peg 708 b (and/or enlarged portions 708 b and/orc) is comprised of a refractory metal (e.g., Rh, Ir, Pd, Pt, and alloysthereof). In certain embodiments, the enlarged portion 708 a comprisesgold, and the remainder of the NFT 708 c and peg 708 b comprise rhodium,and in other embodiments the enlarged portion 708 a and the peg 708 bcomprise rhodium.

As discussed above, an NFT design can involve varying amounts of lowindex dielectric material proximate the NFT. For example, a combinationof dielectric materials can be used proximate the NFT. These variouscombinations are shown below in Table 4 for Design VI of FIG. 7A. Whiledesigns a, d, and e use the same dielectric material to surround theNFT, designs b, c, and f provide partially-wrapped, or sandwichconfigurations, of low-index dielectric material. Also, the NFTconfiguration of Design VI can include adhesion layers 728 between anyand/or all low index refractive material (e.g., silica) layers adjacentthe NFT (e.g., adjacent gold and/or gold alloys and/or Rh). Again, theincreased amount of lower index material (e.g., silica) reduces thetemperature of the NFT at the peg 708 b. Table 4 below shows therespective NFT peg temperature differences for varying combinations ofdielectric materials for Design VI.

TABLE 4 Liner Peg Config- AlO ΔT Ieff uration CDS CNS NPS Sides (3 nm)ATE (K) (mA) Design VI a AlO AlO AlO AlO No 52.9% 330K 5.75 Design VI bAlO AlO SiO₂ SiO₂ Yes 52.5% −30 5.0 Design VI c AlO SiO₂ SiO₂ SiO₂ Yes52.5% −38 4.9 Design VI d SiO₂ SiO₂ SiO₂ SiO₂ Yes 52.5% −48 4.8 DesignVI e SiO₂ SiO₂ SiO₂ SiO₂ No 52.5% −58 4.7 Design VI f SiO₂ AlO SiO₂ SiO₂Yes 52.5% −40 4.9

Table 4 shows the peg temperature change of the respective dielectricconfigurations of materials with respect to a reference temperaturerecorded for the baseline configuration of Design VI a having alumina asthe dielectric. Again, for each design, the temperature of the NFT peg708 b reduced further with increased amounts of lower index materialpresent proximate the NFT. The fully-wrapped design of FIG. 7A (DesignsVI d and e) provided a greater reduction in temperature as compared withthe sandwiched designs of Designs VI b, c, and f. The absence of anadhesion liner between the low index refractive material and theplasmonic material of the NFT further reduced the peg temperature asshown in the comparison of Design VI d and Design VI e. Each of thedesigns reported in Table 4 maintained a down track and cross tracktemperature gradient of 8.3 K/nm, and each of the designs includingsilica (Design VI b-e) maintained an adjacent track erasure (ATE) of52.5%. Notably, as the peg temperature decreases, so does the effectivecurrent required to power the laser diode. This increases the efficiencyof the slider while subsequently improving the reliability andoperational life.

Unless otherwise indicated, all numbers expressing feature sizes,amounts, and physical properties used in the specification and claimsare to be understood as being modified in all instances by the term“about.” Accordingly, unless indicated to the contrary, the numericalparameters set forth in the foregoing specification and attached claimsare approximations that can vary depending upon the desired propertiessought to be obtained by those skilled in the art utilizing theteachings disclosed herein. The use of numerical ranges by endpointsincludes all numbers within that range (e.g. 1 to 5 includes 1, 1.5, 2,2.75, 3, 3.80, 4, and 5) and any range within that range.

The foregoing description of the example embodiments has been presentedfor the purposes of illustration and description. It is not intended tobe exhaustive or to limit the embodiments to the precise form disclosed.Many modifications and variations are possible in light of the aboveteaching. Any or all features of the disclosed embodiments can beapplied individually or in any combination and are not meant to belimiting, but purely illustrative. It is intended that the scope of theinvention be limited not with this detailed description, but rather,determined by the claims appended hereto.

What is claimed is:
 1. An apparatus, comprising: a write pole; awaveguide core; a near-field transducer (NFT) positioned between thewrite pole and the waveguide core, the NFT comprising a heatsinkportion, an enlarged portion, and a peg comprising a refractory metaland extending from the enlarged portion toward a media-facing surface,wherein a first surface of the peg is substantially coplanar with afirst surface of the enlarged portion and the first surface of theenlarged portion shares an interface with the heatsink portion; a firstdielectric layer positioned between the peg and the write pole; a firstadhesion layer positioned between the peg and the first dielectriclayer; a second dielectric layer disposed on an entire surface of theNFT opposing the media-facing surface; and a second adhesion layerpositioned between the NFT and the second dielectric layer.
 2. Theapparatus of claim 1, wherein the first dielectric layer has arefractive index less than 1.5.
 3. The apparatus of claim 1, wherein thefirst and second dielectric layers have a refractive index less than1.5.
 4. The apparatus of claim 1, wherein at least one of the dielectriclayers comprises SiO₂.
 5. The apparatus of claim 1, wherein the firstand second dielectric layers comprise SiO₂.
 6. The apparatus of claim 1,further comprising a third dielectric layer positioned between the NFTand the waveguide core.
 7. The apparatus of claim 6, wherein the thirddielectric layer has a thickness of about 10 to 60 nm.
 8. The apparatusof claim 6, wherein the first, second, and third dielectric layerscomprise the same material.
 9. The apparatus of claim 1, wherein the NFTcomprises a sunken disc.
 10. The apparatus of claim 1, wherein the pegcomprises rhodium.
 11. An apparatus, comprising: a write pole; awaveguide core; a near-field transducer (NFT) positioned between thewrite pole and the waveguide core, the NFT comprising a heatsinkportion, an enlarged portion, and a peg comprising a refractory metaland extending from the enlarged portion toward a media-facing surface,wherein a first surface of the peg is substantially coplanar with afirst surface of the enlarged portion and the first surface of theenlarged portion shares an interface with the heatsink portion; a firstdielectric layer positioned between the NFT and the write pole; and asecond dielectric layer positioned between the waveguide core and theenlarged portion and peg of the NFT, wherein at least the seconddielectric layer has a refractive index less than 1.5.
 12. The apparatusof claim 11, wherein the first and second dielectric layers have arefractive index less than 1.5.
 13. The apparatus of claim 11, whereinthe first and second dielectric layers comprise SiO₂.
 14. The apparatusof claim 11, wherein the second dielectric layer has a thickness ofabout 10 to 60 nm.
 15. An apparatus, comprising: a write pole; awaveguide core; a near-field transducer (NFT) positioned between thewrite pole and the waveguide core, the NFT comprising a heatsinkportion, an enlarged portion, and a peg comprising a refractory metaland extending from the enlarged portion toward a media-facing surface,wherein a first surface of the peg is substantially coplanar with afirst surface of the enlarged portion and the first surface of theenlarged portion shares an interface with the heatsink portion; a firstdielectric layer positioned between the peg and the write pole; and asecond dielectric layer positioned between the NFT and the waveguidecore, wherein the second dielectric layer comprises a bi-layer structurehaving a first dielectric material proximate the peg and a seconddielectric material proximate the waveguide core, wherein at least thefirst dielectric material has a refractive index less than 1.5.
 16. Theapparatus of claim 15, wherein the first dielectric layer comprises thefirst dielectric material.
 17. The apparatus of claim 15, wherein thefirst dielectric material and the second dielectric material aredifferent.
 18. The apparatus of claim 15, wherein the NFT comprises asunken disc and the second dielectric material is positioned between thesunken disc and the waveguide core.
 19. The apparatus of claim 15,wherein the peg comprises rhodium.
 20. The apparatus of claim 15,wherein the first dielectric material is SiO₂ and the second dielectricmaterial is alumina.